Traditionally, cable television systems have delivered entertainment video to subscriber homes. However, in addition to cable television channels, cable systems may provide extended services such as video-on-demand and high-speed internet access. With the expanding usage of the internet and email, the amounts of data being uploaded from subscriber homes is increasing. Sending email attachments or uploading videos or pictures to the web require transferring large amounts of data from subscriber homes back to the cable headend, which requires a considerable amount of bandwidth on the return path. Since the return bandwidth in conventional cable systems is typically restricted to a very narrow band, this often presents a bottleneck that restricts fast and efficient data uploading on the subscriber end.
FIG. 1 illustrates a general schematic of a conventional cable system. System 100 includes a headend 102, a plurality of fibers 104, a plurality of nodes 106, a plurality of coaxial feeder cables 108, a plurality of taps (not shown), a plurality of coaxial cable drops 110, a plurality of amplifiers 112, a plurality of subscriber households 114 and a plurality of terminal equipment 116.
In operation, program content and/or data is received via signals from antenna towers, satellites, or direct fiber links at headend 102. The content is modulated onto an electromagnetic carrier, becoming a radio frequency (RF) signal. At headend 102, each signal is assigned a unique channel frequency that occupies a unique portion of the frequency spectrum. Fibers 104 then transmit the RF energy of the signals as light, from headend 102 down to individual nodes 106. Nodes 106 each then convert the optical signals back to RF signals and transmit them on coaxial feeder cables 108. Along coaxial feeder cables 108 there are various taps (not shown) where the signal is distributed to homes by being “tapped off” to coaxial cable drops 110, which run to individual subscriber households 114 that contain terminal equipment 116 (such as set-top boxes, cable modems, etc). Also, at points along coaxial feeder cables 108, there are amplifiers 112 that amplify the signal to maintain adequate signal strength to other taps down the coaxial cable.
A more detailed representation of a conventional cable system is shown in FIG. 2. System 200 includes a headend 202, a node 204, an RF amplifier 206, a conventional tap 208, a subscriber household 210, a RF amplifier 212, and subsequent taps 214 that continue to an end of the line 216, which include a standard tap with an RF terminating resistor load that maintains a consistent impedance to the coaxial cable. Conventional tap 208 includes a splitter/combiner 218. Subscriber household 210 includes a set top converter 220, a cable modem 221 and a computer 222. For ease of explanation, in FIG. 2 only one node (node 204), one tap (conventional tap 208), and one subscriber household (subscriber household 210) are shown, even though a typical cable system consists of a plurality of nodes, taps, and subscriber households (as illustrated in FIG. 1).
Headend 202 is arranged to communicate bi-directionally with node 204 via a communication line 224 that may include one or more optical fibers. Node 204 is additionally arranged to communicate bi-directionally with RF amplifier 206 via a communication line 226. RF amplifier 206 is arranged to communicate bi-directionally with conventional tap 208 via a communication line 228. Conventional tap 208 is arranged to communicate bi-directionally with subscriber household 210 via a communication line 230. Inside subscriber household 210, communication line 230 is split into communication line 232 and communication line 234. Communication line 232 bi-directionally connects set top converter 220 with communication line 230. Communication line 234 bi-directionally connects cable modem 221 with communication line 230. Cable modem bi-directionally connects computer 222 to communication line 230. Conventional tap 208 is additionally arranged to communicate bi-directionally with RF amplifier 212 via a communication line 236. RF amplifier 212 is arranged to communicate bi-directionally with subsequent taps 214 via a communication line 238.
As mentioned above, headend 202 is operable to receive data from sources (not shown), such as an antenna tower, satellite dish or studio link/feed. Headend 202 is further operable to process the data for transmission to subscriber households, including subscriber household 210. Node 204 is operable to convert optical signals to RF signals. RF amplifier 206 is operable to amplify signals to maintain signal strength. Splitter/combiner 218 within conventional tap 208 “splits” or “taps-off” signals to subscriber household 212, as well as passes the signals to other taps and amplifiers. Similar to RF amplifier 206, RF amplifier 212 is operable to amplify signals to maintain signal strength. Similar to conventional tap 208, conventional taps 214 are operable to “tap-off” signals to other downstream households (not shown).
In operation, headend 202 receives and processes data. Headend 202 then transmits signals “downstream,” i.e., in a direction from headend 202 toward the end of the line 216, via communication line 224 to node 204. Node 204 receives the signals from headend 202, converts the signals and transmits converted signals to RF amplifier 206. Conventionally, communication line 224 is an optical fiber and communication line 226 is a coaxial cable, wherein node 204 converts the optical signals to RF signals. The remainder of communication lines 226, 228, 230, 232, 236 and 238 are conventionally coaxial cables. However, it should be noted that communication lines 224, 226, 228, 230, 232, 236 238 and 239 may be any known form of communication line, non-limiting examples of which include optical fiber, coaxial cable and wireless.
At this point, RF amplifier 206 amplifies the RF signals to maintain signal strength due to the inherent loss in the coaxial cable, before passing the signals to conventional tap 208. As mentioned above, splitter/combiner 218 of conventional tap 208 splits the signals within communication line 226 and provides the signals to subscriber household 210 via communication line 230. Conventional tap 208 distributes to both subscriber household 210 and down communication line 236 to RF amplifier 212 and down stream to other taps and RF amplifiers down the communication line/coax until the end of line tap know as the terminating tap.
The above-discussed transmission, headend to subscriber and terminating tap, of data corresponds to downstream transmissions. In conventional cable systems, data may also travel “upstream,” in a direction from subscriber household 210 back up to headend 202, along the same components, such as RF amplifiers and taps and wires, such as coaxial cable and optical fiber. Since both upstream and downstream signals travel on the same medium, upstream and downstream signals must occupy different frequencies. Typically downstream signals are restricted to a given high-frequency band, but not exclusively, and is denoted as fH, whereas upstream signals are restricted to a given low-frequency band, but not exclusively, and is denoted as fL, wherein fH>fL.
As illustrated in FIG. 2, headend 202 provides signals 240 within high-frequency band fH downstream to splitter/combiner 218. Splitter/combiner 218 splits signals 240 and provides signals 242 within high-frequency band fH to subscriber household 210. Signals 242 are then provided to set top converter 220, cable modem 221 and computer 222. Splitter/combiner 218 additionally provides signals 244 within high-frequency band fH downstream to RF amplifier 212 and subsequent taps 214 and subsequent RF amplifiers (not shown) further downstream.
As illustrated in FIG. 2, either one of set top converter 220 and cable modem 221 is able to send information upstream to headend 202. For example, set top converter 220 may send request information for viewing specific content on demand or may have interactive programming information related to cable television, whereas cable modem 221 may enable computer 222 to upload information via the Internet. Such conventional upstream data is provided in signals 246 within a low-frequency band fL to splitter/combiner 218. Splitter/combiner 218 is additionally able to receive signals 248 within low-frequency band fL from RF amplifier 212 and subsequent taps 214 and subsequent RF amplifiers (not shown) further downstream. Splitter/combiner 218 is operable to combined signals 246 within low-frequency band fL and signals 248 within low-frequency band fL and transmit the combined signals to headend 202 as signals 250 within low-frequency band fL.
In conventional cable systems, the upstream bandwidth is much smaller than the downstream bandwidth. Most cable systems are using an upstream, subscriber to headend, bandwidth of approximately 35 MHz, while the downstream bandwidth is typically around 50 MHz-1 GHz from the headend. The limiting upstream bandwidth is due to the fact that when cable television systems were first implemented in the 1960s, the requirement for a large return bandwidth was not needed at the time. However, since the advent of the internet, there is an ever increasing need for greater return bandwidth. This is due in large part to the increasing amounts of data being transmitted upstream from subscriber households back to the headend, e.g., sending email, uploading of large files such as video, images, music. Returning back to FIGS. 1 and 2, signals 250 within low-frequency band fL may include data supplied from each of subscriber households 114. Thus, the upstream flow of data can easily become a major bottleneck in conventional cable systems. This bottleneck may severely restrict the speed of data uploads from subscriber households 114.
What is needed is a cable system and method that is able to increase the amount of data that can be sent from the subscriber household back to the headend.